Process monitor  and semiconductor manufacturing apparatus

ABSTRACT

A sensor on a semiconductor wafer is used as a process monitor and a capacitor is employed as a power supply for the sensor. The capacitor can be formed by stacking a poly-silicon layer and a silicon nitride layer on the wafer. A timer can be used to specify an operation time or an operation timing, etc. Furthermore, unauthorized use is prevented by storing a keyword in an ROM of the process monitor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 11/819,928, filed Jun. 29, 2007, now U.S. Pat. No. ______, which inturn was a divisional of U.S. application Ser. No. 10/532,991, filedApr. 28, 2005, now U.S. Pat. No. 7,303,928, which was a U.S. nationalstage application of international patent application no.PCT/JP2003/012555, filed Sep. 30, 2003, which claims benefit of Japanesepatent application no. 2002-318116, filed Oct. 31, 2002, the entiredisclosures of each of which are hereby incorporated by reference intheir entirety.

FIELD OF THE INVENTION

The present invention relates to a process monitor for monitoring asemiconductor manufacturing process, such as a plasma process, and to asemiconductor manufacturing apparatus having a process monitor.

PRIOR ART

Conventionally, in a semiconductor manufacturing apparatus, ameasurement of a plasma density or a temperature, etc., to optimallycontrol a plasma process is carried out, for example, by inserting aplasma probe or a thermocouple into a plasma processing chamber at atime of development in a factory. However, as high-mix low-volumemanufacture increases in LSI manufacturing, process conditions are madedifferent and the plasma state must be measured each time the processchanges. If, at each time, measuring by inserting a probe or the like iscarried out, the measurement is very troublesome and a wiring, formeasurement and control is necessary, which causes a disturbance in ameasuring object. A simultaneous multipoint measurement is difficult andmeasurement at an area where the measurement is actually required isalso difficult. Furthermore, a problem of contamination or a problem ofdecrease in operating rates, arises.

Recently, a sensor wafer, which is a sensor having no probe and can becarried in the same way as a normal silicon wafer, has been developed(see, for example, Yan Tran, Tim Yen and Bruce Bunn (UCLA) “Developmentof Lithium Batteries for Powering Sensor Arrays”, SFR Work shop, Nov.14, 2001).

However, a battery, which is a power supply source for the wafer sensor,is deteriorated by repeated charging and discharging. A material ofwhich the battery is made could contaminate a plasma processing chamberif the sensor wafer is broken by an unexpected accident or the like.

Disclosure of the Invention

The object of this invention, in view of the above-mentioned problems,is to provide a process monitor having a battery, which is hardlydeteriorated and has no fear of contamination, and a semiconductormanufacturing apparatus having the process monitor.

To accomplish the object, a capacitor is employed as a power source ofthe process monitor for monitoring the process by a sensor wafer. Acapacitor is not deteriorated by repeating charging and discharging aslong as an insulating film does not change its nature. A material, whichdoes not contaminate a process chamber, can be selected as materialwhich constitutes the capacitor. For example, the capacitor can be madeby stacking a poly-silicon layer and a silicon nitride layer.

The process monitor according to the present invention can comprise amemory to store measured data and further an timer to set an operatingtime and an operating period of the process monitor in order to make itwork in specific state.

Furthermore, an unauthorized use can be prevented by storing a keywordin an Read Only Memory (ROM) of the process monitor.

A semiconductor manufacturing apparatus according to the presentinvention having the process monitor, comprises at least one of ahousing unit to store the process monitor, a charger to charge acapacitor, that is a power supply and a reader/writer for measured data.

Moreover, semiconductor manufacturing apparatus according to the presentinvention can compare the measured data read by the reader/writer withpredetermined reference data and can control the manufacturing processin a predetermined way, if the measured data exceeds a predeterminedrange of the reference data.

The process monitor according to the present invention uses a capacitoras a power source. The capacitor can be hardly deteriorated and,therefore, there is no fear of contaminating a process chamber. Further,data for only a specific period of time can be obtained by using atimer. Further, unauthorized use can be prevented because a keyword ischecked when reading data. The semiconductor manufacturing apparatusaccording to the present invention uses the process monitor to monitorthe manufacturing process without fear of contamination or decrease inoperating rates and indicates appropriate maintainance for theapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a process monitor according to the presentinvention.

FIG. 2 is a view of one embodiment of a charging means for a processmonitor according to the present invention.

FIG. 3 is a view of one embodiment of a capacitor as a battery of aprocess monitor according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of this invention will be explained with reference to thedrawings.

FIG. 1 is a schematic view of a process monitor according to anembodiment of this invention. The process monitor, in FIG. 1, isprovided with nine sensors 21 to 29 each 10 mm square, arrangedcrosswise on a surface of a semiconductor wafer 1 having a diameter of,for example, 300 mm. In this embodiment, multilayer capacitors 11 and12, which are connected in series to serve as a power source, arearranged at two places of the wafer 1 and are used as a power source formeasurement by the sensors and reading the measured signals. Thecapacitors are charged and discharged through the charging anddischarging terminals 31 and 32 connected with positive and negativeelectrodes of the capacitors. Whether the capacitors are connected inseries or in parallel can be appropriately determined, in accordancewith required capacity, withstand voltage or the like.

Furthermore, a timer 5 and a controller 4 are provided. The timer 5 canspecify a starting and ending time of the measurement or a time periodof the measurement. The controller 4 can control the measurement byusing the sensor. Further, the controller 4 can control the writing orreading action of the measured signals into or from a storage device andtransmission or receipt of signals to or from an external device.

Moreover, a memory 6, which is to store the measured data, and an ROM 7are arranged as memory devices. Data, representing the plasma statedetected by the sensors 21 to 29, is stored in the data memory 6. Datasignals can be taken to an external device through I/O terminals 41 and42. In the ROM 7, keywords or passwords to identify the process monitorare stored.

FIG. 2 shows a charging operation of the capacitor of the processmonitor by way of example. A three dimension movable component 30′having terminals 31′ and 32′, corresponding to the charging anddischarging terminals 31 and 32 of the capacitor, respectively, isarranged in a charging unit provided, for example, in a cassettechamber. Charging is carried out when connection to the terminals isestablished. Likewise, the I/O terminals 41 and 42 are connected toterminals of a component provided in a data reading unit to obtain datasignals.

FIG. 3 shows an example of the capacitor that works as a power supply inthis embodiment. Although the capacitors are arranged at two places ofthe wafer in FIG. 1, it is assumed that one capacitor is arranged inFIG. 3.

The capacitor is fabricated on a substrate S of a Si wafer bymicro-machining. Semiconductor circuits for the measuring operations andsignal transmission and receipt, such as a measurement control IC,memories for measured data (SRAM, DRAM, EEPROM or the like) and othercircuits required for the process monitor, not shown in the drawings,are integrated on the substrate S.

On the substrate S, insulating layers D₁ to D_(n-2) and wiring layers M₁to M₂ are formed and the capacitor is formed by dielectric layers D₂ toD_(n-3) placed between electrodes E₁ to E_(n-3) formed on wiring layersM₃ to M_(n-1). The electrodes E₁ to E_(n-3) are made of poly-silicon,and the dielectric layers D₂ to D_(n-3) are made of silicon nitride.Terminals T₁ and T₂ correspond to the charging and discharging terminals31 and 32 in FIG. 1. The terminal T₁ is connected to the electrode M₃formed on the wiring layer M₃ through a via hole extending through thewiring layers. The terminal T₂ is connected to the electrode E_(n-3)formed on the wiring layer M_(n-1). The terminals T₁ and T₂ can be madeof Al or can be made of poly-silicon. If used for a sensor for anetching process of Si, the terminals may be made of a material such asTi or W. Although the number of the multi-layers constituting thecapacitor can be determined appropriately, the number is usually in therange of 10 to 100 layers.

Any known method can be used to manufacture a capacitor bymicro-machining. In this embodiment, conductors of the wiring layer Mare made with Al. Al is applied to a front surface and is thereafterremoved by etching, etc., and an insulating layer is buried in theremoved portion. Although other wiring, which connects the upper andlower layers electrically, is established through via holes made with W,materials other than W can be used. Other proper materials can be alsoused for the electrodes and the dielectric constituting the capacitor.The capacitor can be various in form. It is also possible to form theportions constituting the capacitor separate from other components, sothat only the capacitor is formed by a multi-layer structure.

Next, operations to monitor the plasma processes in the semiconductormanufacturing apparatus having the process monitor according to anembodiment of the present invention, will be explained.

Although any type of known semiconductor manufacturing apparatus can beused, an apparatus will be explained by way of example. The apparatushas, besides the plasma processing chamber, a cassette chamber, analignment chamber and a transfer robot chamber, in which a wafer to beprocessed is placed in the cassette chamber, carried from the cassettechamber through the alignment chamber to the plasma processing chamber,carried back to the cassette chamber after processing.

The process monitor, that is a sensor wafer, is stored in the cassettechamber of the semiconductor manufacturing apparatus. The cassettechamber is provided with a charging unit to charge the capacitor as apower supply of the sensor wafer and with a reading unit to readmeasured data. If it is necessary to measure the plasma conditions ofthe process chamber, for example, before a lot production begins, in thesame way as transfer of a normal wafer from the cassette chamber, theprocess monitor, which has been charged and is ready to measure, istaken out by a transfer robot, carried, introduced into the processchamber, placed on a susceptor and then the measuring process is carriedout. The operation of the sensor is per se known and a plasma densityand a plasma temperature, etc., are measured according to apredetermined measuring process. As a measuring time is usually in therange of 1 to 30 minutes, the operation can be performed using the powerfrom the capacitor on the semiconductor wafer.

The sensor wafer of the embodiment has also a timer, which makes itpossible to select a specific measuring time such as starting time,intermediate time or ending time. This means that data for a specificperiod of time, not averaged data over the whole process period, can beobtained. This is very useful, because, for example, in a process, inwhich an element is damaged due to instability of the plasma upon plasmaignition, the data only at the plasma ignition can be obtained.

Note that a chamber where the sensor wafer is stored and charging iscarried out, is not limited to the cassette chamber. The transfer robotchamber or the alignment chamber can be used for that purpose or achamber only for the sensor wafer can be provided. Further, a timer canbe set when charging the capacitor.

In some cases, the sensor wafer may be placed on the wafer cassettetogether with a normal wafer to be processed, and is removed after theplasma process ends.

After measurement, the sensor wafer is returned to the cassette chamberand, if necessary, is connected to an external power supply through thecharging and discharging terminals 31 and 32. Data stored in the memory6 is read through the I/O terminals 41 and 42. In case of reading thedata, the reading operation cannot be carried out unless a specifickeyword or password stored in the ROM 7 of the sensor wafer can be readby the data reading unit. This prevents an unauthorized use of thesensor wafer.

A control unit to change the manufacturing conditions or to requiremaintenance, based on the measured data, can be provided. Namely, adatabase, which contains data being previously obtained and evaluatedregarding the plasma, is provided in the semiconductor manufacturingapparatus or an external server. The measured data, read from the sensorwafer by the control unit, is compared with data from the database inthe semiconductor manufacturing apparatus or the external serverconnected thereto by means of communication.

If a comparison result between the data in the database and measureddata exceeds the range of a reference, the control unit can change theoperation condition of the semiconductor manufacturing apparatus ortransmit a signal to stop the apparatus and request maintenance. In anycase, it is possible to prevent a product yield from decreasing.Further, if the sensor wafer is used without an authorization, nomeasured data to be compared can be obtained. Alternatively, the readingunit can transmit dummy data for the measured data.

In this embodiment, transmission and receipt of signals, the charging orthe like is carried out through the I/O terminals or the charging anddischarging terminals, respectively. However, signals can be transmittedor received through wireless or infrared rays and the power can besupplied to the capacitor using a contactless technique.

1. A process monitoring apparatus for monitoring a semiconductormanufacturing process, comprising: a container element; a monitorelement including a wafer and a plurality of sensors attached to thewafer, the monitor element being able to be transferred into targetenvironments in a process facility or into the container element by atransfer robot; and an electronics module attached to the containerelement, the electronics module being available for communication withthe monitor element when the monitor element is transferred into thecontainer element.